Re: Generic hash function?

Tom Lane wrote:

>Brian Hurt <bhurt(at)janestcapital(dot)com> writes:
>
>
>>I'm trying to write a generic equals operator that works on type
>>anyelement,
>>
>>
>
>What for? You'd ultimately have to depend on the various actual input
>types' native equality operators, so I don't see what this'd buy except
>a layer of useless-seeming overhead. Also, it could only be hashable
>if the input type's equality is hashable, and we don't have any way to
>deal with a "sometimes hashable" equality operator.
>
> regards, tom lane
>
>
>
>

What I'd like to write is:

CREATE FUNCTION eqnull(anyelement, anyelement) RETURNS BOOLEAN AS $_$
SELECT
(CASE
WHEN $1 IS NULL AND $2 IS NULL THEN TRUE
WHEN ($1 IS NULL AND $2 IS NOT NULL)
OR ($1 IS NOT NULL AND $2 IS NULL)
THEN FALSE
ELSE $1 = $2
END
)
$_$ IMMUTABLE LANGUAGE SQL;

Which changes how nulls are handled. This makes writing certain kinds
of queries much easier and much more clear what the query is doing.

Am I going to need to create an operator class for every type?

Brian